From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk1-x730.google.com (mail-qk1-x730.google.com [IPv6:2607:f8b0:4864:20::730]) by sourceware.org (Postfix) with ESMTPS id 5E8E13858C39 for ; Wed, 6 Oct 2021 19:19:28 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 5E8E13858C39 Received: by mail-qk1-x730.google.com with SMTP id c7so3688665qka.2 for ; Wed, 06 Oct 2021 12:19:28 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=2Txr+6O+Va+hvJjdPYvB4Wts5V86fo0rmSY2YgsL4VQ=; b=LymdjvVhvTl6Q3qNbneY2vVLVBHLyR05TK+P+oL9b5A3gYSEJ6a9RlwinqPbuOmr6q V6/CqgRYmi+xp3jrk1o8xIIZrDvXJDb9DvtIk6wU53Kr876rNQfPqJ683/R4zSN8CIOp QdO0ogw/kNcgMMtXOiDt6jbGCBNVIz4+OBCjT/DA6OCECwrRzXZa5MSyR0S/lO0sfv+W nnuxUqH+H7QasQyAS8D04J3cNS61X8EuwG+W9JTWD7JoImWl5YKLCz2wSmkZH/iAglGc wzZSA+xkm4oO9hLJqQkejyARiff9Zpla3w2M+kuiSej0jV0LkB7rwAq7qVtykO1jAPbJ F8OQ== X-Gm-Message-State: AOAM533YVXL4Ixcjeg8iLatWaayPYLaOHjr2yoMDthOYa+nyvMs3NYTi pJDGTRfz4QbABoBC38lDmdkvfd21jXry2g== X-Google-Smtp-Source: ABdhPJxN/cTpCasGVor8hclUbt1tHZ8bUJxMelqkNLpmHieplZpXsqoGukiUIYNYdu6EW6nL2dWWDg== X-Received: by 2002:a37:8401:: with SMTP id g1mr422349qkd.231.1633547967817; Wed, 06 Oct 2021 12:19:27 -0700 (PDT) Received: from ?IPv6:2804:431:c7cb:807a:2ebe:4b13:27bd:f11d? ([2804:431:c7cb:807a:2ebe:4b13:27bd:f11d]) by smtp.gmail.com with ESMTPSA id u189sm12036405qkh.14.2021.10.06.12.19.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 06 Oct 2021 12:19:27 -0700 (PDT) Subject: Re: [PATCH 8/9] i386: Move hypot implementation to C To: Joseph Myers Cc: libc-alpha@sourceware.org References: <20211006180557.933826-1-adhemerval.zanella@linaro.org> <20211006180557.933826-9-adhemerval.zanella@linaro.org> From: Adhemerval Zanella Message-ID: <6d85d3c2-3c4d-dc3b-e87c-141968f947b9@linaro.org> Date: Wed, 6 Oct 2021 16:19:25 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-7.7 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 06 Oct 2021 19:19:29 -0000 On 06/10/2021 15:37, Joseph Myers wrote: > On Wed, 6 Oct 2021, Adhemerval Zanella via Libc-alpha wrote: > >> +/* The i386 allows ot use the default excess of precision to optimize the > > s/ot/to/ Ack. > >> + hypot implementation, since internal multiplication and sqrt is carried >> + with 80-bit FP type. */ >> +double >> +__ieee754_hypot (double x, double y) >> +{ >> + if ((isinf (x) || isinf (y)) >> + && !issignaling (x) && !issignaling (y)) >> + return INFINITY; >> + if (isnan (x) || isnan (y)) >> + return x + y; >> + >> + double r = math_narrow_eval (sqrt (x * x + y * y)); > > There is no guarantee of when excess precision might or might not be used > for intermediate computations, or whether it might not be used (so > resulting in spurious overflows). I'd expect explicit conversions of x > and y to long double here, use of sqrtl and conversion of the result to > double. > Something like the below? long double lx = x; long double ly = y; double r = sqrtl (lx * lx + ly * ly); return r;